Preheat oven to 375 degrees F. Place potatoes in large saucepan, cover with water and bring to a boil. Reduce heat and cook potatoes until tender, about 15 minutes. Cut broccoli heads into small florets and place on baking tray. Drizzle with olive oil and roast for 15 minutes. Drain cooked potatoes in a colander. In the saucepan, combine the flour and melted butter; cook on medium heat for 1 minute. Slowly add milk to the mixture, stirring constantly until thickened. Soup can be thinned by adding an additional 1/2 cup of milk or water, if desired. Add the potatoes, broccoli, salt, pepper, cheese, half of the green onions and bacon bits. Cook on low until heated. A few minutes before serving, add the sour cream and stir to combine. Serve topped with remaining onions.